Effect of nanoscale curvature sign and bundle structure on supercritical H2 and CH4 adsorptivity of single wall carbon nanotube

The adsorptivities of supercritical CH(4) and H(2) of the external and internal tube walls of single wall carbon nanotube (SWCNT) were determined. The internal tube wall of the negative curvature showed the higher adsorptivities for supercritical CH(4) and H(2) than the external tube wall of the positive curvature due to their interaction potential difference. Fine SWCNT bundles were prepared by the capillary force-aided drying treatment using toluene or methanol in order to produce the interstitial pore spaces having the strongest interaction potential for CH(4) or H(2); the bundled SWCNT showed the highest adsorptivity for supercritical CH(4) and H(2). It was clearly shown that these nanostructures of SWCNTs are crucial for supercritical gas adsorptivity.ArticleADSORPTION-JOURNAL OF THE INTERNATIONAL ADSORPTION SOCIETY. 17(3):643-651 (2011)journal articl

Dehydrogenation of ammonia borane confined by low-density porous aromatic framework

Ammonia borane (AB) has been considered as an outstanding candidate material for on-board hydrogen storage due to its high stoichiometric hydrogen content (19.6 wt %) and moderate dehydrogenation temperature. However, slow dehydrogenation kinetics below 100 C and release of volatile byproducts (ammonia, borazine, and diborane) limited its practical applications. In this work, low-density and highly porous aromatic framework (PAF-1; BET, 4657 cm g; pore volume, 2.55 cm g) was utilized as a template for the first time to nanoconfine AB molecules. The dehydrogenation behavior of the confined AB was studied by temperature- programmed desorption mass spectrometry (TPD-MS) and pressure-composition- temperature (PCT) analyses. It was found that the AB molecules can be fully confined within the nanopores when the weight ratio of AB/PAF-1 is around 1:1. More importantly, AB started to dehydrogenate at very low temperature (around 50 C) with the peak of 77 C in the absence of any volatile byproducts such as ammonia, borazine, or diborane. Furthermore, about 4 wt % of hydrogen was evolved in the first 25 min at 75 C which is 27 times higher than the pristine AB, displaying higher kinetics at low temperatures. Compared with other porous supports such as MOFs, the PAF-1 has a very low framework density because it is built up only by light C and H elements. This could significantly improve the hydrogen systemic gravimetric capacity of the AB-confined system and thus increase feasibility in practical applications